Transcript What is a Rocket? - MiddleSchoolEngineering2010

• What is a Rocket?
A chamber enclosing
a gas under pressure.
A release nozzle directs
escaping air in one focused
direction
 A balloon is a simple
example of a rocket.
Rubber walls compress the air inside.
Air escapes from the small opening at
one end and the balloon flies.
Newton’s Three Laws
1. Objects at rest will remain at rest and
objects in motion will remain in motion
in a straight line unless acted upon by an
unbalanced force.
2. Force equals mass times acceleration.
3. Every action has an equal and opposite
reaction.
1. Objects at Rest, in Motion
Force of
GRAVITY
At Rest: Forces are balanced.
The force of gravity on the
rocket balances with that of
the launch pad holding it up.
In Motion: Thrust from the
Note:
Thrust from
the rocket’s
engines acts
downward
producing an
upward
reaction on
the rocket
rocket unbalances the forces.
As a result, the rocket travels
upward (until it runs out of
fuel).
REACTION
from
Thrust
2. F=mA
Force equals mass times
acceleration. The pressure
created inside the rocket acts
across the area of the bottle’s
throat and produces force (thrust).
Mass represents the total mass of
the rocket, including its fuel.
The mass of the rocket changes
during flight. As fuel is rapidly
used and expelled, the rocket
weighs less and accelerates.
Thrust continues until the engine
stops firing.
Mass
F
o
r
c
e
Acceleration
Thrust Force
produced as fuel rapidly
exits, accelerates rocket.
3. Action and Reaction
A rocket takes off only when
it expels gas. Action: The
rocket pushes the gas out of
the engine. Reaction: The
gas pushes up on the rocket.
The Action (Thrust) has to be
greater than the weight of the
rocket for the reaction (liftoff)
to happen.
UP
(Bottle & Water Mass) X
(Bottle Velocity)
EQUALS
(Ejected Water Mass) X
(Ejected Water Velocity)
DOWN
Essentially, the faster the
fluid is ejected, and the more
mass that is ejected, the
greater the reaction force
on the bottle.
TRAJECTORY
Trajectory is the curved path of an object traveling through space.
NOTE: Even objects thrown or launched vertically have a trajectory.
Trajectory Path
Apogee
(Highest Point of Trajectory)
(Launch Angle)
X
(Distance Traveled)
Factors that Affect Bottle Trajectory:
• Newton’s 3 Laws of Motion
• Flow Rate of Fuel Existing
- Bottle Internal Pressure
- Air/Fuel Volumes
- Air/ Fuel Densities
• Mass of Bottle
• Air Resistance/Drag Affects
- Atmosphere Pressure/Temp
- Bottle Aerodynamics
• Gravity
Roll motion
• The rolling motion can be caused by the
deflection of the fins of the rocket. The fins
can be hinged like the rear section of an
airplane wing. Deflecting the rear section
changes the aerodynamic shape of the fin and
generates a lift forceperpendicular to the flight
direction
Pitch
• he pitching motion is being caused by the
deflection of the nozzle of the rocket. Such a
rotation of the nozzle is calledgimballing
Possible fin designs- note symmetry
Step 1: Cut a Circle
out of thick stock paper
or thin poster material
(Using 16” or larger
diameter).
Step 2: Cut a line
along the radius
as shown.
Uniform Fit AllAround Here
Step 3: Rotate the paper
into a cone. Next Tape or Glue
the seam to maintain the cone’s
shape. You can adjust the angle of the cone
with more rotation.
(Keep in mind that the base of your
Step 4: If needed trim the
cone needs to be large enough
base of cone as required so
to fit around the top of the
that it has a uniform fit with
pressure vessel).
the diameter of a 2L bottle.
Diagram 1
Rocket Identification
Min Cone Radius = 0.5 inches
Ballast Added to the
Nose Cone (e.g. Styrofoampeanuts, shredded paper, etc.)
Nose Cone
Bottle Height
(max. 30 inches)
Pressure Vessel
(Clear 2 Liter Bottle)
Fin
Rocket Clear of Any
Coverings (min. 3 inches)
Fin
Bottle Throat
Throat Exit
Plane
Fins Start
(min. 4 inches)